The invention relates to hearing aids, and more particularly relates to circuits used in hearing aids. In its most immediate sense, the invention relates to modular in-ear hearing aid circuit structures from which a plurality of hearing aid models, particularly programmable models, may be assembled.
Hearing aid manufacturers offer an entire line of hearing aids. Each model incorporates a particular type of hearing aid circuit. When a dispenser fits a patient with a hearing impairment, the dispenser selects the particular hearing aid model having the circuit that best addresses the patient's needs.
Conventionally, hearing aid circuits are built up by hard-wiring discrete components together. As a result, hearing aid manufacturers are required to maintain a relatively large inventory of electronic components and subassemblies and to train manufacturing personnel to assemble those parts in many different configurations. These steps are costly.
Additionally, in-ear aids (ITE "in the ear" aids; CIC "completely in canal" aids; and canal aids) are custom-manufactured for the patient and therefore can vary widely in their physical configurations. This variation requires that the manufacture of the hearing aid circuit be highly customized to the intended application and such customization adds to manufacturing cost.
It would therefore be advantageous to provide a modularized hearing aid circuit that would reduce the number of different electronic subassemblies that must be maintained in inventory.
It would also be advantageous to provide a modularized hearing aid circuit that could, using a limited number of modules and physical configurations, be configured to constitute any one of the circuits in the manufacturer's line of hearing aids.
In accordance with one aspect of the invention, first and second battery terminals and first and second circuit boards are provided. Each of the terminals is supported by a corresponding one of the circuit boards. The circuit boards form a support having a plurality of support stations, for supporting a like plurality of additional circuit boards of rectangular shape and common width. The terminals are so located that a hearing aid battery inserted into the hearing aid contacts both of the battery terminals.
In accordance with this aspect of the invention, hearing aid circuits and circuit options (e.g. an amplifier circuit, a programmable control circuit, filter circuits, switching circuits etc.) are mounted on additional circuit boards, which are in turn mounted upon the support. This makes it easy to produce a hearing aid of the desired model merely by selecting the necessary components and mounting them (in the preferred embodiment, as many as four of them) upon the support.
In accordance with another aspect of the invention, which is particularly advantageous for use with programmable hearing aids, a multi-electrode strip is also provided. The additional circuit board (or boards) is (or are) electrically connected to this strip. In the preferred embodiment of this aspect of the invention, the distal end of this strip is terminated with programming terminals. This makes it possible to program the programmable control circuit using an external programmer.
In the preferred embodiment, at least one, and perhaps both, of the first and second circuit boards are provided with a capacitor. This permits a very large capacitance to be placed across the hearing aid battery. This is advantageous because when the battery is substantially discharged, the impedence of the battery can greatly increase the current drawn by the circuit during operation.